Advances in digital signal processing (DSP) have led to a proliferation of hardware (HW) and software (SW) developments/solutions that have been applied to various audio systems ranging from traditional 2.1 up to virtual 7.1 audio systems including headphones/headsets. In particular, by taking advantage of these new DSP technologies to a great extent, there have been a significant number of changes in headphones/headsets. Users of headphones, headsets and ear buds are seeing virtualized 5.1 and 7.1 versions come to market. These expanded versions require a lot more audio/sound processing power to achieve audio (sonic) results desired, which closely approximate actual 5.1 and 7.1 sounds, and to achieve optimized audio for gaming purposes.
FIG. 1 shows a top view of a schematic diagram of a user 100 wearing a headphone (or headset) 102. The head-related transfer functions (HRTFs) at the right ear cup 104 and the left ear cup 106 of the headphone 102 are represented by HRR 108 and HLL 110, respectively which are used to denote the direct transmission or audio impulses that the right ear and the left ear would respectively perceive. Ideally, in a contained environment, there should be no crosstalk between the right ear cup 104 and the left ear cup 106, i.e., the HRTF from right to left ear cups (HRL 112) and the HRTF from left to right ear cups (HLR 114) are zero. The right ear cup 104 and the left ear cup 106 are independent from each other. However, it should be understood that in practice, audio signals may have inherent crosstalk that may affect the sound perceived by the user.
While advances in HRTF implementations have been realized, they are based on “fixed models” of implementations. This means that these implementations are not adaptive and do not take into account ambient noise or the physical aspect of a human listener's (or user's) ear(s). The listener's outer ear configuration or structure (or pinna) can compound the problem by way of applying an “amplification and/or attenuation factor”, which is related to the human hearing sensitivity, to the incoming audio signature (or signal). FIG. 2 shows a schematic diagram of the listener's ear 200. The pinna 202 of the listener's ear 200 acts as a receiver for the incoming audio signal 204 through the auditory canal 206 into the tympanic membrane 208. Because of the spreading out of sound energy by inverse square law, a larger receiver, for example, a large pinna 202 picks up more energy, amplifying the human hearing sensitivity by a factor of about 2 or 3.
Due to the fixed nature of current HRTF implementations it is not possible to account for and adjust for the variables that are known to exist regardless of environment, for example, ambient noise, variability in size and shape of the outer/inner ear canals of a given listener, variable positions of the audio driver(s) in the headset, for example, the headset 102 of FIG. 1 in relation to the outer/inner ear canal.
Thus, there is a need to provide a method and apparatus for integration within audio devices such as headphones, headsets and ear buds a real-time adaptive audio adjustment system that would significantly improve the perceived sound quality; thereby seeking to address at least the above mentioned problems.